1. Field of the Invention
The present invention relates to a transfer member (transfer sheet) of an image forming material for electrophotography for forming (recording) a fine image on an image recording member using an electrophotographic image forming device. The invention also relates to a member having an image recorded thereon, a method for producing a member having an image recorded thereon by using the transfer member, and an apparatus for producing the member having an image recorded thereon using the transfer member. More specifically, the invention relates to a transfer member (sheet) of an image forming material for electrophotography for forming a printed image, a method for producing a member having an image recorded thereon using the same, an apparatus for producing a member having an image recorded thereon, and a member having an image recorded thereon which are used for image-containing bodies such as non-contact type or contact-type information recording media including personal information and image information, e.g., a cash card with a facial portrait, an employee ID card, a student ID card, a personal membership card, a residency ID card, various driver's licenses and various qualification certificates, an RFID tag, an image sheet for identification for use in medical institutions or the like, an image display board, a display label or the like.
2. Description of the Related Art
Recently, as image forming technologies have developed, means for forming images having the same quality in large numbers and at low cost by various printing methods such as image intaglio printing, surface printing, planography, gravure printing and screen printing have been known. Such printing methods are used frequently for the preparation of information recording media that include predetermined information and are capable of communicating with an outer device in a contact or non-contact manner, such as an IC card, a magnetic card and an optical card, or a combination thereof.
However, for example, the above screen printing requires many printing plates corresponding to the number of images to be printed. Furthermore, in the case of color printing, more printing plates are additionally required corresponding to the number of colors. Accordingly, these printing methods are not suitable for dealing with individual personal information for identification (e.g., facial portraits, legal names, addresses, dates of birth, various licenses or the like).
The current mainstream of image forming means for dealing with the above-mentioned problems includes image forming methods using a printer employing a sublimatic or a melt-type heat transfer system using an ink ribbon or the like. Such methods can easily print personal information for identification, but still have problems in that resolution decreases with an increase in printing velocity and in that printing velocity decreases with an increase in resolution.
Furthermore, for the heat transfer system, methods for printing on an image recording member using an intermediate transfer member have been disclosed (see, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 5-096871, 7-068812, 8-142365, 8-156302, 9-314875 and 11-291646). However, in each case, a thin colored layer transferred from an ink sheet is formed on the surface of an intermediate transfer member, and unless this colored layer is firmly transferred to the image recording member, fine image quality cannot be obtained. In addition, since the image quality is basically determined by concavity and convexity of the surface of the image recording member, the image quality is maintained by providing a rubber-like elastic layer on the intermediate transfer member so as to increase the adhesion to the image recording member, adhering firmly by pressure, and transferring the image. The surface layer of the intermediate transfer member is basically designed so as to have releasing property, but a rigid surface layer cannot be used because the surface layer is required to follow the above rubber-like elastic layer. Accordingly, silicone or fluorine rubber is specifically used for the surface layer.
On the other hand, image forming (printing) by an electrophotographic system is carried out by a method of uniformly charging the surface of the image recording member, exposing the surface of an image recording member according to an image signal, forming an electrostatic latent image by potential difference between the exposed portion and the non-exposed portion, and statically developing color powder (image forming material), which is called toner and has the opposite (or the same) polarity to that of the charged potential to form a visible image (toner image) on the surface of the image recording member surface. A color image is obtained by a method of repeating the above-mentioned steps several times, or a method of placing plural image forming devices in parallel to form color visible images, and transferring and fixing (fixation: fixing mainly by fusing of color powder by heat and cooling thereof) these images onto the image recording member to provide a color image.
As mentioned above, according to the electrophotographic system, an electrostatic latent image is electrically formed on the surface of the image recording member using an image signal. Therefore, not only can the same image be formed repeatedly, but the method can easily deal with different images to carry out image formation. Furthermore, the toner image on the surface of the image recording member can be transferred almost completely to the surface of the transfer member or the image recording medium, and residual traces of the toner image remaining on the surface of the image recording member can be easily removed using a resin blade, a brush or the like. Accordingly, printed articles to be produced in various kinds and in small amounts can be easily produced.
The toner is generally formed by melt mixing a hot melt resin and a pigment, along with additives such as an antistatic agent when necessary, and grinding the kneaded product to form microparticles. Furthermore, since the electrostatic latent image obtained in the electrophotographic system has higher resolution than that of the microparticulated toner, more sufficient resolution can be expected as compared with the resolution obtained by the above-mentioned screen printing or heat transfer system using an ink ribbon.
For the color image, quality of color similar to that obtained by printing can be reproduced theoretically by mixing color toners of the four elementary colors of cyan, magenta, yellow and black. Furthermore, since toner resins and pigments can be mixed relatively freely for the color toners, image masking property by the toners can be easily enhanced.
In addition, heat resistance and light resistance of an information recording medium assuming outdoor use has been investigated little. Specifically, when a driver's license is placed in direct sunlight in a vehicle, a heat-transfer type image using a dye as a color material is decolorized. On the other hand, in the case of a color image formed by an electrophotographic system, the light resistance of the image formed by the electrophotographic system is considered to be sufficiently excellent because the color toner comprises pigments having excellent light resistance corresponding to the colors of cyan, magenta, yellow and black. Similarly, it is considered that the heat resistance of the image formed on the information recording medium can be increased to the level that allows outdoor use by choosing and using a toner having heat resistance.
Moreover, a substrate (core) most frequently used for various cards at the present time is a vinyl chloride sheet, since it has excellent printing property and excellent embossing suitability (concavity and convexity treatment for letters or the like) for use in conventional printing machines. However, the vinyl chloride sheet has a problem in that dioxin is generated when cards disposed due to expiration or the like are burned in a heating furnace or the like. Accordingly, in view of effect on the environment, various sheet films are currently used for the purpose of excluding use of vinyl chloride.
For the preparation of a card, based on the presupposition that embossing is not carried out, a conventional biaxial oriented PET (polyethylene terephthalate) film or the like can be used. However, in many cases, embossing is indispensable for maintaining the conventional functions of cards. Accordingly, an ABS resin film and a polyolefin resin film, which soften at relatively low temperature, a modified PET resin film called as PETG, which is obtained by copolymerizing at least ethyleneglycol, terephthalic acid and 1,4-cyclohexanedimethanol, an integrally-molded film of a modified PET resin film and a PET film, amorphous PET resin film or polycarbonate resin film or the like are currently used.
As an example of a method for printing on various cards using the above-mentioned electrophotographic apparatus, for example, JP-A No. 2001-92255 discloses a method of printing an invisible barcode as well as personal information on a vinyl chloride sheet having a thickness of 250 μm or a polyester sheet having a thickness of 280 μm by electrophotographic means, superposing an overcoat film on the printed surface, and laminating the film using a heat press.
However, the above-mentioned sheet has poor sheet conveying property because the frictional coefficient between the sheets is too high and the sheets adhere firmly. Therefore, the electrophotographic apparatus stops, and in the case where the above-mentioned insulator (sheet) having a thickness of no less than 250 μm is used, the image forming material (toner) is difficult to transfer sufficiently, which sometimes leads to increased deficiency of an image. Furthermore, when the resin film that softens at comparatively low temperature is used for the electrophotographic apparatus to try to form an image, there arises a problem in that adhesiveness property is exhibited during the step for fixing because the fixing temperature is higher than the softening temperature of the film, and the film winds around the fixing device and causes jamming. In addition, when the image forming material offsets on the fixing device or when the fixing of the sheet having a thickness of not less than 250 μm is continued, the fixing device is unnecessarily damaged by edges of the sheet, which frequently requires replacement of components.
As another example, JP-A No. 11-334265 discloses a method for printing personal information for identification on a light transmission sheet in which the printing is carried out using a mirror image. However, the document merely discloses that the light transmissive laminate sheet is preferably a film at least a part of which comprises a biaxial oriented polyester film, ABS or polyester (a biaxial oriented polyester film) and that vinyl chloride may be used.
Accordingly, since the film is merely an insulating material in this document, transfer deficiency of the image forming material on the film surface or the like may occur, and a similar level of resolution to that obtained by a heat transfer system or the like cannot be obtained. Furthermore, since this device puts emphasis on the improvement of productivity and the laminate sheet used for the device has a rolled shape, there arises a problem in that great loss and waste are generated upon dealing with the production of urgent matter or various kinds or the like, such as different printing for cards for one to several persons.
Furthermore, when an information recording medium is produced using the above laminate sheet, plural sheets are superposed, which provides a thick recording medium as a whole. For example, when an information recording medium having a thickness of about 800 μm is used, the above-mentioned method sometimes cannot deal with the demands of the medium.
In addition, automation of a step for conveying and stacking a laminate sheet or the like on which an image has been fixed and a plastic substrate and a step for laminating, as well as a step for forming an image on a laminate sheet, have been investigated little. Therefore, in view of improvement of productivity, further design of the above steps and the production device is required.